There are various designs in existence for providing ventilation for the areas beneath building roofs. The ventilation of such areas is desirable to reduce the accumulation of heat in the summer, and to reduce the accumulation of moisture during all times of the year. In providing ventilation, it is important to prevent the entry of water into the structure through the vent. Also, it is desirable to prevent debris and small animals from entering the structure through the vent.
Existing off-ridge roof vent designs are available in various configurations. One such design consists of simply a duct having a baffle mechanism over the top to prevent the entry of rain into the structure. A variation of this simple design is the turbine type roof vent, which consists of a rotating element on the exterior of the duct and interior baffles to prevent the entry of water into the building. However, both such designed provide only a limited area through which air and moisture may escape from the structure. Also, such designs typically extend a considerable height from the surface of the roof, making them vulnerable to being knocked from the roof by tree limbs, wires, or simply the wind itself.
Other designs fit more closely to the surface of the roof, and provide a long rectangular opening through which air and moisture may exit the structure. Generally, a slot is cut in the roof that is slightly smaller than the foot print of the vent. The slot then communicates with a passageway that, in profile, is generally in the shape of an inverted J. Thus, the opening of the vent faces down, towards the roofing surface. In this way, water is prevented from entering the structure. Such vents may also be provided with a mesh or screen covering the opening, to prevent the entry of debris or small animals into the structure.
However, existing low profile designs suffer from a number of disadvantages. For example, such designs are vulnerable to damage by wind or by impacts from debris. This is because the relatively large area of the opening is unbraced throughout the center of the vent. As a result, even relatively mild winds are capable of exerting sufficient force to damage the device. Typically, damage from the wind to such vents is in the form of bent or deformed top pieces or hoods. Such damage makes the vent more easily penetrated by rain and debris, because portions of the vent opening are enlarged, and often results in deformation of those portions of the vent that interface with the surface of the roof, thus interfering with the proper sealing of the vent to the roof surface. Damage from debris or from careless workers walking on the roof often occurs as crushed or otherwise inwardly deformed top pieces or hoods. This type of damage impedes the movement of moisture and air through the vent and is unsightly. In addition, existing vents can be deflected by the wind or forces to an extent short of what is required to cause permanent damage to the vent. However, such deflection is undesirable for several reasons. Where the opening of the vent is enlarged, rain may more easily enter the structure through the vent. Where the opening of the vent is made smaller, the movement of air and moisture through the vent is impeded. Also, existing designs have a top piece or hood which offers little clearance between itself and the interior baffle, limiting the amount of air that can move through the slot.
Although the prior art describes designs for providing through-roof ventilation to structures, it would be advantageous to provide a design which provided a vent that resists deflection and bending caused by the wind or other forces. In addition, it would be advantageous to provide such a design which had a low profile, and which offered a relatively unimpeded flow of air and moisture from the area beneath the roofing surface to the outside atmosphere.